Declare variable before using it

theano/sandbox/scan.py

@@ -199,6 +199,8 @@ def scan(fn,
         actual_slice = seq[0]
         _seq_val = tensor.as_tensor_variable(seq)
         _seq_val_slice = _seq_val[0]
+
+        nw_slice = _seq_val_slice.type()
         # Try to transfer test_value to the new variable
         if config.compute_test_value != 'off':
             try:
@@ -212,7 +214,6 @@ def scan(fn,
                         'the inner function of scan, input value '
                         'missing %s'), e)
 
-        nw_slice = _seq_val_slice.type()
         if seq.name:
             nw_slice.name = seq.name + '[t]'
         scan_seqs.append(_seq_val)